Artificial finger elements are available which can be used as integral parts of hand- or arm-prostheses. They orientate in their form and its motility to a finger.
From DE 309 367 hand-prostheses with multi-member thumb- and forefinger-elements, that work against each other, are already known from the time of the First World War. The single finger joints are positioned via a gearing with tooth sector and threaded screws, wherein the drive is carried out via cable pulls and lever mechanisms out of the thenar. A motoric drive is not envisaged, as well as an individual motility of single fingers.
Even the DE 323 970 dated 1919 discloses such a rotation mechanism for a phalanx.
Hand-prostheses with a motoric rotation drive for two fingers against each other are disclosed for instance by DE 26 07 499 C3 and U.S. Pat. No. 4,094,016. A geared motor as control member is arranged in these concepts in the thenar-area of the prosthesis.
However, the mentioned systems do not enclose any autarkic driven finger elements, wherein all control members which are necessary for the operation are enclosed in the finger element. The drives are in these systems arranged outside the finger elements. Thus, they are conceptually not suited for the use as single-finger-prosthesis. Also the use as component in a prosthesis-modular-system is substantially restricted by that.
In contrary, the DE 698 16 848 T2 as well as the DE 198 54 762 C2 respectively disclose a finger element, each with a motoric rotation drive with a threaded screw and a gearing per hinge. The motors are arranged directly in the phalanges.
However, in these finger elements, the worm gear is fixed permanently to the motor shaft, such that in case of an applied load of the finger element high forces may affect the motor. An early drive- or motor-damage as well as a blocking of the worm drive under load is abetted therewith.
Constructions as described for instance in DE 319 092 A and US 2005 0021154 A1, wherein the movements of the distal phalanges may be achieved via stiff push- and pull-rods which are all but not elastic, appear mostly to be unrealistically robot-like and are not suited in particular for sensitive picking problems. Also in this case early overload symptoms have to be expected.
In contrary, in WO 2007/063266 A1 a hand-prosthesis with moveable finger elements is described, wherein a decoupling of drive shaft and threaded screw is realized via a bevel gear transmission arranged in between with a direction change of the rotation movement of about a right angle.
With the latter concept a mechanic partial decoupling of worm wheel and drive shaft and therefore a mechanic load revealing of the last named is disclosed, but in connection with additional components and/or a larger construction volume. The construction volume limits the use as single-finger-prosthesis in particular for the replacement of smaller fingers enormously by esthetic reasons.